Method of producing offset printing plate

ABSTRACT

An offset printing plate of improved printability is provided utilizing the silver complex salt diffusion transfer process by treating an offset master plate containing an image-receiving layer composed of 100 parts by weight of a physical development center and not more than 30 parts by weight of a high-molecularweight compound, with a transfer developer solution consisting essentially of a developing agent, a solvent for a silver halide, and at least one organic heterocyclic compound such as 3-pentylbenzoxazoline-2-thione, 5-phenyl-2-mercapto-1,3,4-oxadiazole or 3-mercapto-4-methyl-5-pentyl-1,2,4-triazole.

[ METHOD OF PRouUCmG OFFSET 3,702,246 11 1972 Ohyama 96/76 PRINTING PLATE 3,671,242 6/1972 Liebe.... 96/29 3,394,005 7/l968 Blake.... 96/67 [75] Inventors: Shigeyoshi Suzuki; Norio Kobayashi;

Klyosh Futakl an of Kyoto Japan Primary ExaminerNorman G. Torchin [73] Assignee: Mitsubishi Paper Mills, Ltd, Assistant ExaminerJohn L. Goodrow Marunouchi, Chiyoda-ku, Tokyo, AttorneyRichard C. Sughrue et al. Japan [22] Filed: Mar. 30, 1972 57 ABSTRACT [21] Appl. N0.: 239,756

[30] Foreign Application Priority Data Mar. 20, 1971 Japan 46 19001 [52] U.S. Cl 96/29 L,-96/76 R [51] Int. Cl G03c 5/54 [58] Field of Search 96/29 R, 76, 67,

[56] References Cited UNITED STATES PATENTS 3,063,837 11/1962 Lassig 96/29 L An offset printing plate of improved printability is provided utilizing the silver complex salt diffusion transfer process by treating an offset master plate containing an image-receiving layer composed of 100 parts by weight of a physical development center and not more than 30 parts by weight of a high-molecular-weight compound, with a transfer developer solution consisting essentially of a developing agent, a solvent for a silver halide, and at least one organic heterocyclic compound such as 3-pentyl-benzoxazoline-2-thione, 5-phenyl-2-mercapto-l,3,4-oxadiazole or 3-mercapto- 4-methyl-5 -pentyll ,2,4-triazole,

7 Claims, No Drawings 1 METHOD OF PRODUCING OFFSET PRINTING PLATE BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention relates to a method of producing an offset printing plate of improved printability using a transfer developer solution containing a certain organic compound.

2. Description ofthe Prior Art The production of offset printing plates is based on the principle of bringing an image of an original impressedon a silver halide photographic sheet (negative) into contact'with an image-receiving sheet (positive), which is produced by coating a supportwith a dispersion of colloidal particles of a heavy metal or its sulfide or oxide (physical development center) in a hydrophilic high-molecular-weight compound as a binder, in a transfer developer solution consisting-essentially of a developing agent and a solvent for the silver halide, whereby reduced metallic silver is precipitated in the positive layer to form an impressed image. In addition to such an offset master two sheet type, there is another type in which an offset master monosheet formed by coating a dispersion of a physical development center in a. hydrophilic high-molecularweight compound as a binder on a silver halide emulsion layer on a support is exposed image-wise with'visible lightrays, and the resulting latent image is' developed.

Japanese Pat. Publication No. 14330/67 discloses a transfer developer solution for offset printing plates comprising hydroquinone or phenidone as a developing agent and sodium thiosulfate as a solvent for a silver halide as the main ingredients and further containing sodium hydroxide, sodium sulfite (anhydrous), or potassium bromide. There is also known a transfer developer solutionof the same composition except containing benzotriazole in place of potassium bromide (Jap anese Patent Publication No. 20505/61). These developer solutions, however, have failed to give offset printing plates having utilitarian values (good printability). The resultant offset printing plates. cannot give clear impressionsunless a considerable number (more than 100) of copies are allowed to run freely beforehand, or unless the properties of ink, an etching liquid, and a dampening liquid are fully controlled, the ink adheres the to hydrophilic part, or the nonimage areas of the printed paper are contaminated. Furthermore, there is the disadvantage that because of insufficient density of printing, irregularity in density occurs during the print ing of a number of copies.

SUMMARY OF THE INVENTION It has now been found that the above defects can be completely eliminated by improving the transfer developer solution for use in producing offset printing plates.

According to this invention, there is provided a method of producing an offset printing plate utilizing the silver complex salt diffusion process which comprises treating an offset master plate containing an image-receiving layer composed of 100 parts by weight of a physical-development center and not more than parts by weight of a high-molecular-weight compound, with a transfer developer solution comprising a developing agent, asolvent for a silver halide and at least one organic compound expressed by any of the, following formulae wherein R, is a lower alkyl group; R is a member se- .lected from the group consisting of a hydrogen atom,

lower alkyl groups and alkoxy groups; R, is a member selected from the group consisting of lower alkyl groups, aryl groups and substituted aryl groups; X is DESCRIPTION OF THE PREFERRED EMBODIMENT The offset printing plate according to this invention is produced utilizing the silver complex salt diffusion transfer process, and basically, the method of this invention is applicable to two types of offset master plate. In one of these types, a negative sheet and a positive sheet are formed on separate supports, respectively.

The negative sheet is prepared by coating a silver halide gelatin emulsion of either low sensitivity for contact printing orihigh sensitivity for photographing on a wa ter-proof paper or synthetic resin film. This type of master plate is characterized by the positive sheet which is prepared by applying a surface layer composed of fine particles of a heavy metal or its sulfide, etc. as a physical development center and O to 30 percent, based on said physical development center, of a high-molecular-weight compound to a synthetic resin film or water-proof paper rendered hydrophilic beforehand, said fine particles of the physical development center being at least partially exposed from the surface.

The other type contains a negative layer and a positive layer, i.e., an image-receiving layer, on onesupport. It

weight compound in order to obtain superior offset printing properties.

Any of these types, when treated in accordance with the method of this invention, becomes an offset printing plate with the formation of an oleophilic silver image on the image-receiving layer.

The developing agent includes those commonly used as a reducing agent for photographic development. Specific examples are aromatic organic compounds such as phenidone, hydroquinone, Metol, pyrogallic acid, Pyramidol, hydramine, amidol, paraamidophenol, protocatechuic acid, or pyrocatechin. The solvent for a silver halide, as is well known, refers to a substance which has an action of dissolving silver chloride, silver bromide, silver iodide, etc. and is used as a fixation agent in the field of photography. Specific examples include sodium thiosulfate, sodium sulfite, potassium cyanide, thiourea, ammonium thiocyanate, ammonium thiosulfate, sodium thiocyanate, or thiosinamine, the first two being frequently utilized in the field of photography. The amount of the developing agent is 3 to 20 g per liter of the developer solution, and the amount of the solvent for silver halide is 5 to 30 g per liter of the developer solution.

The critical feature of this invention is that at least one organic compound of the above formulae (1) to (Ill) having an -SH group or a group as a basic part is added as a third component of the transfer developer solution. The general formulae (l) to (ill) cover a wide range of organic compounds that can equally be used in this invention, and it is difficult to describe each and every compound that comes within these formulae in the present specification. However, the especially preferred compounds are shown below.

(1) O 3-pentyl-benzoxaz0- line 2 thione.

N I s u (2).. NBC CQHS 4-benzamlde-3- I mercapt0-5-n- N pentyl-1,2,4-

triazole. ]1-C5Hu-C fi-S (3).. S 3-ethyl-benzothiazoline-2-thlone.

(4).... O 5-phenyl-2-mercapto- 1,3,4-oxadlazole. (i3 I(ZT S H (5).. O 5-propyl-2-mercapto- 1,3,4-0xadlnzola. C;H1-C ([f- S H (6).... S 3-methyl-benzothluzollne-Z-thlone.

(7) 0 5-methyl-2-mercapto- 1,3,4-oxadlazolo. CH;C (5-8 (8)--- S 3-pro yl-benzothiazolne-2-thl0ne.

/C=S C3117 (9) 0 S-(p-methylphenyD- 2-mercapto-1,3,4- CH3- (l (H3SH oxadiazole.

(l0) S H 1-phenyl-5-mercapto- I 1,2,3,4-tetrazole. Q") N=N (11) 0 H, 1,3-diethylbenzimidaz- I oline-2-thlone.

i CzH;

(l2) C H; 3-mercapto-4-methyl- Ilq 5-pentyl-L24-trlazo1e. C5H11-C C-SH (13)... NH-C O-GH; 3-mercapto-4-aceta- I mlde-5-n-heptyl- N 1,2,4-triazole. l1-C7H15-C CSH ll ll (14)... S 3,6-dlmethyl-benzothlaz0line-2-thionc.

I CH;

(15)... S 3-ethyl-6-ethoxybcnZothlaZollne-Z- C thione.

F Cal-I5 (16)..- NH: 3-mereapto-4-amino- 5-n-pentyl-1,2,4- triazole.

Il-CsHn-C fi-SH (17)..- S H 1-ethyl-5-mercapto- Cl1 1,2,3,4-tetrazole. Call -1H1 lfiI =VN It is to be understood that the organic compounds used in this invention include all known compounds expressed by the formulae (l) to (Ill) having a or an -SH group as a basic part, which produce results equivalent to those of the above-cited specific compounds, and therefore that the present invention is not limited to the above-specified compounds alone.

These organic compounds are typified substantially by. heterocyclic compounds such as polyazoles, imidazoles, thiazoles, thiazolines, thiazolidines, oxazble s, oxadiazoles, or imidazolines. Since these organic compounds are very difficultly soluble in water, it is preferred to add them to an aqueous solution of an alkali metal hydroxide or ammonia with apH of 8-12 or dissolve them in a water-miscible organic solvent such as alcohols, e.g., methanoLethanol or propanol, ketones, e.g., acetone, diacetone or acetonylacetone, formamide, dimethyl formamide, or dimethyl sulfoxide prior to use for production of the transfer developer solution. The amount of the organic, compound to be used is preferably 0.05 to 1.00 g per liter of the develvarious additives known in the art, such as pyridinium salts, hydrazines, or amines.

Theuse of the transferdeveloper solution described above makes it possible to produce anoffset printing plate ofgood printability (giving more than several thousand good impressions from a single plate), which permits economical printing without free running at the initial stage and can give impressions of high density and great aesthetic finish. The offset printing plates obtained by treating offset master plates with the transfer developer solution described hereinabove, especially those based on the application of the silver complex salt diffusion transfer process in which the imagereceiving layer comprises not more than 30 parts by weight of the high-molecular-weight compound and 100 parts by weight of the physical development center, find a wide range of practical applications, and far excel other printing plates of the same kind.

The invention will now be described further by the following examples.

EXAMPLE 1 0.2% AgNO 10 cc 1 KBr 1 cc 2 formalin 10 cc 0.03N NaOH 100 cc Water was added to the above ingredients to adjust the total amount to 200 cc (percent above is by weight) to form a silver sol. Water-proof raw paper with-a surface which had been treated with a 5 percent gelatin aqueous solution was coated with the resulting sol to form an offset master plate (the method described in Japanese Pat. application No. 72039/69). A similar silver sol can be applied by dip coating a synthetic resin film which has been rendered hydrophilic before-hand. The offset master p late so obtained was cut into proper length. lts surface and NL (commercially available negative sheet for the silver complex salt diffusion transfer process) exclusively used for Mitsubishi Hishirapid PF were placed opposite to each other, and treated with a peeled off, and the positive sheet could be directly used for offset printing without post-treatments such as rinsing. The treatment temperature was 15 to 30 C.

Sodium hexametaphosphoric acid 1 g l-lydroquinone 24 g l-Phenyl-3-pyrazolidone 2 g Sodium sulfite (anhydrous) 150 g Sodium thiosulfate 28 g Potassium bromide 3 g Potassium hydroxide 12 g Sodium hydroxide 12 g 2-Phenyl-5-mercapto-oxadiazole 0.2 g

4-Benzamide-3 -mercapto-5-pentyl-1,2,4-triazole Water to make 1 liter The developer solution had been diluted with an equivalent quantity of water before application.

The offset printing plate obtained was mounted on an offset printing machine (AM 1250W, or Model 321 of AB. Dick Company), and printing was performed immediately, using a known offset printing dampening liquid such as ammonium secondary phosphate, CMC, glycerol, or sodium nitrate hexahydrate as an aqueous solution, and water as an etching liquid at a printing speedof 150 impressions per minute. Impressions which were clear and suffered little contamination were obtained from the outset. On the other hand, when the above transfer developer solution was replaced by a known transfer developer solution, the printing plate exhibited poor ink receptivity until more than impressions were obtained, and the impressions obtained were useless because of great contamination.

EXAMPLE 2 The same offset master plate as obtained in Example 1 was developed with a transfer developer solution of the following recipe.

l-Phenyl-3-pyrazolidone 1.0 g

Sodium sulfite (anhydrous) 75.0 g

Hydroquinone 10.0 g

Sodium hydroxide 15.0 g

Sodium thiosulfite (crystals) 50.0 g

Potassium bromide 2.0 g

3rPropyl-benzothiazoline-2-thione 0.10 g

5-Propyl-2-mercapto-1,3,4-oxadiazole 0.05 g

Water to make 1 liter The resulting offset printing plate was mounted on a known offset printing machine, and printing was performed using water both as a dampening liquid and an etching liquid. More than several hundred clear impressions were obtained by free running only several copies at the start. The impressions obtained were of high density, and the image reproduction was of high fidelity. 5

When the transfer developer solution did not contain 3-propyl-benzothiazoline-Z-thione and 5-propyl-2-mercapto-l,3,4-oxadiazole, the resulting offset printing plate did not produce an increased printing effect, and suffered from the thinning and excessive adhesion of printing ink with wasteful consumption of more than 100 copies by free running.

EXAMPLE 3 An aqueous solution containing metal silver in an amount of 0.1 percent as silver sol was coated on a commercially available enlarging copying film (e.g.,

HlSl COPY CHF of Mitsubishi Paper-Making Co. Ltd.) prepared by coating a silver chlorobromide photographic emulsion on a 100 u-thick polyethylene terephthalate film pre-treated with a primer. The resulting film plate was developed with a developer solution of the following recipe after photographing an original by a camera using a commercially available enlarging machine.

Hydroquinone 12 g l-Phenyl-3-pyrazolidone 10 g Sodium sulfite (anhydrous) 60 g Potassium hydroxide 12 g Potassium bromide 15 g Sodium thiosulfate 10 g 3Methyl-benzothiazoline-Z-thione 0.15 g

3Propylbenzothiazoline-2-thione 0.15 g

5-( p-Methyl-phenyl )-2-mercapto-l ,3,4-oxadiazole lPhenyl-5-mercapto-l,2,3,4-tetrazole 0.05 g

The above ingredients had been diluted with water to adjust the total amount to 1 liter, and further diluted with an equivalent amount of water. Then, the same procedure as set forth in Example 1 was repeated, and the same results as set forth in Example 1 were obtained.

EXAMPLE 4 The same offset master plate as used in Example 1 was developed with a transfer developer solution obtained by replacing the last four ingredients of the developer solution in Example 3 by 0.05 g of l-ethyl-2- mercapto-benzimidazole and 0.10 g of 3-mercapto-4- acetamide-S-n-heptyll ,2,4-triazole.

The resulting offset printing plate was subjected to the printing test using commercially available offset printing inks (3-1010 of AB. Dick Company, F Gross of Dai-nippon lnk Co., and Speed King of Toyo lnk Co., Ltd.). There was hardly any experimental difference among these three types of printing ink, and more than 500 very clear impressions of high density and beautiful finish were obtained with free running of about 10 copies at the start.

On the other hand, when the conventional transfer developer solution was used, the resulting printing plate varied in printing effect according to the types of printing ink (ranging from one similar to the present invention to an extremely impractical one). This will demonstrate that the offset printing plate obtained by the method of this invention has great improvement over the conventional one, and finds versatile applications.

EXAMPLE 5 Using a negative plate for the silver complex salt diffusion transfer process produced by coating a silver halide photographic emulsion on a polyethylene laminate paper (see Japanese Pat. publication No. 143 30/67), the same offset master plate as used in Example was developed with a transfer developer solution of the following recipe. The resulting offset printing plate was directly mounted on an offset printing machine. At this time, pure water with a pH of about 6.8 was used as a dampening liquid, and 100 g of an aqueous solution of 30 g of ammonium secondary phosphate, 2 g of CMC and l g of a copolymer of polyvinylmethyl ether and maleic anhydride was used as an etching liquid.

Recipe of the Developer Solution Hydroquinone 10 g l-Phenyl-3-pyrazolidone 15 g Sodium sulfite (anhydrous) g Sodium thiosulfate 40 g Sodium hydroxide 15 g Potassium bromide 2.0 g

4-acetamide-3-methyl-S-mercaptol ,2,4-triazole l,3diethyl-benzimidazoline-2-thione 0.05 g

The above ingredients were diluted with water to adjust the total amount to 1 liter, and the solution was further diluted with an equivalent amount of water.

The same procedure as set forth in Examples 1 and 4 was then repeated. It was found that the offset printing plate thus obtained exhibited performance comparable to PS plate for versatile applications to produce a greater number of impressions.

What is claimed is:

l. A method of producing an offset printing plate utilizing the silver complex salt diffusion transfer process, which comprises treating an offset master plate containing an image-receiving layer composed of parts by weight of a physical development center and not more than 30 parts by weight of a high-molecularweight compound, with a transfer developer solution consisting essentially of a developing agent, a solvent for a silver halide and at least one organic compound of the following formulae:

wherein R, is a lower alkyl group; R is a member selected from the group consisting of a hydrogen atom, lower alkyl groups and alkoxy groups; R; is a member selected from the group consisting of lower alkyl groups, aryl groups and substituted aryl groups; X is O-, S- or 1'11 a- .a... ...:N- a

and Y is O,

NH; NH-C O-Ra Il a ,illjf fli -N-- benzothiazoline-Z-thione,

5. The method of claim 1, wherein the amount of said solvent for a silver halide is 5 to 30 g per liter of the developer solution.

6. The method of claim 1, wherein said developing agent is selected from the group'consisting of phenidone, hydroquinone, Metol, pyrogallic acid, Pyramidol, hydramine, amidol, para-amidophenol, protocatechuic acid and pyrocatechin.

7. The method of claim 1, wherein said solvent for a silver halide is selected from the group consisting of sodium thiosulfate, sodium sulfite, potassium cyanide,

thiourea, ammonium thiocyanate, ammonium thiosulfate, sodium thiocyanate, and thiosinamine. 

2. The method of claim 1, wherein said organic compound is selected from the group consisting of 3-pentyl-benzoxazoline-2-thione, 4-benzamide-3-mercapto-5-pentyl-1,2,4-triazole, 3-ethyl-benzothiazoline-2-thione, 5-phenyl-2-mercapto-1,3,4-oxadiazole, 5-propyl-2-mercapto-1,3,4-oxadiazole, 3-methyl-benzothiazoline-2-thione, 5-methyl-2-mercapto-1,3,4-oxadiazole, 3-propyl-benzothiazoline-2-thione, 5-(p-methyl-phenyl)-2-mercapto-1,3,4-oxadiazole, 1-phenyl-5-mercapto-1,2,3,4-tetrazole, 1,3-diethylbenzimidazoline-2-thione, 3-mercapto-4-methyl-5-pentyl-1, 2,4-triazole, 3-mercapto-4-acetamide-5-n-heptyl-1,2,4-triazole, 3,6-dimethyl-benzothiazoline-2-thione, 3-ethyl-6-ethoxy-benzothiazoline-2-thione, 3-mercapto-4-amino-5-n-pentyl-1,2,4-triazole and 1-ethyl-5-mercapto-1,2,3,4-tetrazole.
 3. The method of claim 1, wherein the amount of said organic compound is from 0.05 g to 1.00 g per liter of the developer solution.
 4. The method of claim 1, wherein the amount of said developing agent is 3 to 20 g per liter of the developer solution.
 5. The method of claim 1, wherein the amount of said solvent for a silver halide is 5 to 30 g per liter of the developer solution.
 6. The method of claim 1, wherein said developing agent is selected from the group consisting of phenidone, hydroquinone, Metol, pyrogallic acid, Pyramidol, hydramine, amidol, para-amidophenol, protocatechuic acid and pyrocatechin.
 7. The method of claim 1, wherein said solvent for a silver halide is selected from the group consisting of sodium thiosulfate, sodium sulfite, potassium cyanide, thiourea, ammonium thiocyanate, ammonium thiosulfate, sodium thiocyanate, and thiosinamine. 